Ukrainian President Volodymyr Zelenskiy speaks at a news briefing in Kyiv , Ukraine, February 24, 2022. Ukrainian Presidential Press Service/Handout via REUTERS
Ukrainian President Volodymyr Zelenskiy speaks at a news briefing in Kyiv , Ukraine, February 24, 2022. Ukrainian Presidential Press Service/Handout via REUTERS Reuters / Ukrainian Presidential Press Ser

The United States believes Russia's invasion of Ukraine is designed to decapitate Ukraine's government and one of the three main axes of assault is directed at the capital Kyiv, a senior U.S. defense official said on Thursday.

After President Vladimir Putin declared war in a pre-dawn televised address, explosions and gunfire were heard throughout the morning in Kyiv, a city of 3 million people.

The assault brought a calamitous end to weeks of fruitless diplomatic efforts by Western leaders to avert war, their worst fears about Putin's ambitions realized.

"The indications we've seen thus far, in just these first, not even 12 hours, are in keeping with our assessment earlier, that would be his goal: to decapitate this government," the official told reporters, speaking on condition of anonymity.

The official did not provide evidence.

The official said this appeared to be only the first phase of a large-scale Russian invasion that so far has used a limited number of the more than 150,000 Russian troops arrayed around Ukraine.

"We don't believe he has committed anywhere near a large portion of the forces that he has available to him," the official said.

Previously, U.S. officials had told Reuters that a Russian invasion could last 10-15 days but this official declined to speculate on how long the Russian onslaught would last, saying putting a timetable on it would be "a fool's errand."

The Russian attack has included more than 160 missile launches by Russia so far, including short-range ballistic missiles, as well as medium-range missiles, cruise missiles and surface-to-air missiles.

There has been no indication of any amphibious assaults yet by Russian forces, despite early media reports, but they used about 75 military aircraft in the first phase of the invasion, the official added.

"The targets, thus far ... have been primarily focused on military and air defense. So barracks, ammunition warehouses, nearly 10 airfields targeted," the official said.

The U.S. official detailed three main axes of the Russian attack: 1) a Russian advance south into the northern Ukrainian city of Kharkiv, the site of the heaviest fighting so far; 2) a push north out of Russian-controlled Crimea to the southern Ukrainian city of Kherson; 3) Two lines of Russian assault southeast and southwest from Belarus toward the capital Kyiv.

The official said Russian forces had made advances on Kyiv.

The Kremlin's early push toward Kyiv supports the U.S. view the Russians aim to install "their own method of governance."

"These three axes are ... clearly designed to take key population centers," the official said. The senior defense official said the United States had not seen an increased threat with regards to Russia's nuclear forces.

The United States is sending 7,000 troops to Germany to help reassure NATO allies, some part of a larger contingent that had already been put on alert earlier this year, the official added.

President Joe Biden referred to these troops in a speech earlier on Thursday. There are already about 90,000 U.S. troops in Europe and Biden has made clear they will not be going into Ukraine to fight Russian forces.

The U.S. official said the United States had seen indications that Ukrainians were fighting back and the invasion had the potential for massive bloodshed.

"It has every potential to be very bloody, very costly and very impactful on European security writ large."